The invention relates to a terminal for a radiation conductor for medical and, especially, dental applications, for example, and a lens for use at the end of a light conductor from which the light emerges, more particularly.
A terminal for a laser light conductor is disclosed in West German patent publication No. 21 45 921. It is intended to increase the divergence of the laser beam from the light conductor only relatively slightly and transmit high radiation powers with only low losses in the terminal while remaining convenient to manipulate. For this, specifically, the terminal tapers from its ends to its middle. The terminal is to be used with a focusing lens on the end of the light conductor from which the laser beam emerges for cutting and coagulating tissues and the like in medical applications, in addition to other purposes.
However, the terminal has the same, round cross section as the laser light conductor with which it is used and, therefore, emits the light in a beam also having a round cross section. As a result, the light beam impinges on a surface as a radiation field for use either normally in a round spot, which is too small and/or non-corresponding to the use intended, or obliquely in an oval spot, which necessarily introduces intensity variation along the major axis and is prone to shadows on uneven surfaces for further intensity variation. Both are undesirable for many uses. For example, in dentistry, it may be desirable to cure a material along a row of teeth with ultraviolet radiation. This requires an elongated, generally rectangular radiation field thereon with, preferably, uniform intensity thereover for uniform curing.
Masks have also been used to make a radiation field rectangular. This is necessarily inefficient, however, because of the radiation lost on the mask.